No abstract

1. Insects are sensitive to climate change. Consequently, insect‐mediated ecosystem functions and services may be altered by changing climates.2. Dung beetles provide multiple services by burying manure. Using climate‐controlled chambers, the effects of warming on dung burial and reproduction by the dung beetle Sisyphus rubrus Paschalidis, 1974 were investigated. Sisyphus rubrus break up dung by forming and rolling away balls of manure for burial and egg deposition.3. To simulate warming in the chambers, 0, 2 or 4 °C offsets were added to field‐recorded, diurnally fluctuating temperatures. We measured dung ball production and burial, egg laying, survival and residence times of beetles.4. Temperature did not affect the size or number of dung balls produced; however warming reduced dung ball burial by S. rubrus. Because buried balls were more likely to contain eggs, warming could reduce egg laying via a reduction in ball burial. Warming reduced the humidity inside the chambers, and a positive relationship was found between the number of dung balls produced and humidity in two temperature treatments. Temperature did not affect survival, or whether or not a beetle left a chamber. Beetles that did leave the chambers took longer to do so in the warmest treatment.5. This study demonstrates that climate warming could reduce reproduction and dung burial by S. rubrus, and is an important first step to understanding warming effects on burial services. Future studies should assess warming effects in field situations, both on individual dung beetle species and on aggregate dung burial services.

To preserve insect-mediated ecosystem services under ongoing climate change, it is necessary to first understand the impact that warming will have on the insects that provide or mediate these services. Furthermore, because responses of a species may be modified by interactions with competitors, it is informative to examine warming effects on organisms and service provision under competition. Dung beetles provide numerous services to agriculture by burying the manure of other animals. To understand the potential impacts of climate warming on ecosystem service provision, we exposed two dung beetle species (Sisyphus rubrus and Euoniticellus fulvus (Coleoptera: Scarabaeidae)), occurring together in the same experimental pats, to warming and measured reproduction (dung ball production and burial, brood production, and egg laying), pat departure behaviour and survival of both species. These two species are likely competitors in pastures in northern New South Wales. To simulate climate warming, we used custom-built chambers to add offsets (+0, +2 or +4°C) to field recorded, diurnally fluctuating baseline temperatures. There was no direct effect of increased temperature on any measured trait in either species. We did find however that the relative survival of the two species depended on temperature; S. rubrus had a higher probability (resulting in greater odds) of surviving than E. fulvus in the +0 and +4°C offset chambers, but not in the +2°C offset chambers. Likewise, the relative likelihood of the different species leaving a dung pat was temperature dependent; in the +2°C offset chambers, E. fulvus were more likely to leave than S. rubrus, but not in the +0 and +4°C offsets chambers. Our results highlight that it may be important for future studies to consider warming effects on relative survival and emigration because such effects could potentially lead to changes in dung beetle species composition.

1. Both larval and adult dung beetles depend on dung resources for nutrition. The quality of the dung resources utilised by beetles can influence adult morphology, adult biomass, and life history parameters of dung beetles. Although several studies have compared dung nutrients of different vertebrate dung types, variation in dung nutrients over time has been less studied.2. Here, moisture content and chemical parameters of dung were analysed at monthly intervals over 12 months. The reproductive output of Onthophagus binodis fed dung collected at four different months of the year is also measured to assess the relationship between dung resources and dung beetle performance. The experiments were carried out under controlled conditions: 25 ± 1 ∘ C: 15 ± 1 ∘ C (L: D) and 60 ± 5% RH, respectively, with a photoperiod of 14L:10D.3. Over the 12-month sampling period, the maximum number of broods and highest brood weight were observed from beetles utilising dung collected in the Austral summer (February 2018). The analysis of dung over the 12-month period showed that the electrical conductivity and phosphorous, manganese, and magnesium content of dung were highest in February 2018.4. The results suggest that the variation in dung resources, such as moisture and minerals, across the year affected the reproductive performance of Onthophagus binodis, which was highest when beetles were provisioned with summer dung.

Dung beetles provide economically valuable ecosystem services to agriculture. Dung beetles are also sensitive to climate change, which may impact on the services that they provide. Using climate-controlled chambers, we investigated the potential effects of climate change on the performance of a tunnelling dung beetle, Onthophagus taurus. Over two trials, we exposed beetles to a +0°C, +2°C or +4°C increase in diurnally fluctuating field recorded temperatures and measured survival, pat departure, reproduction (brood number and size) and dung burial by beetles. Temperature treatment did not affect pat departure behaviour. Relative to the control +0°C chambers, beetle survival was higher in the +2°C chambers, but there was no difference in survival between the +0°C and +4°C chambers. In Trial 1, brood number was reduced in both the +2°C and +4°C chambers, relative to the +0°C chambers. In Trial 2, brood number was significantly reduced relative to control chambers in the +2°C chambers only. Temperature did not affect brood size. Across temperature treatments, there was a significant, positive relationship between brood number and dung burial. However, trends in brood production with temperature were not mirrored by dung burial; the only reduction in dung burial was found in the warmest treatment of Trial 2. Our results suggest that initially, warming may not substantially reduce dung burial by O. taurus; however, ecosystem services may be impacted if lower brood production eventually reduces beetle numbers. Studies such as ours identify the vulnerabilities of ecosystem service providers to climate change and in doing so are an essential first step in the management of ecosystem services under future warming.Austral Entomology (2020) 59, 353-367 bs_bs_banner † These traits were binary variables, i.e. a beetle left a chamber via the emergence trap or remained, and a beetle survived or died.Warming effects on tunnelling dung beetles 355